Many wheels for passenger and off-road vehicles generally comprise a center bore that at least partially receives the end of the axle when the wheel is secured to a hub assembly surrounding the axle. The center bore can be carefully sized to receive and support the axle, and hence the weight of the vehicle, while the lug nuts and threaded studs hold the inner face of the wheel against a hub flange. While some wheel designs leave the center bore and the tip of the axle exposed to ambience, other wheel designs cover the center bore with a hub cap or center cap that serves to prevent or limit moisture, oil, grease, dirt and sand from coming into contact with the center bore, and possibly working their way into the clearance between the end of the axle and the inside cylindrical surface of the center bore to cause damage or premature wear to the outer surface of the axle or the inside cylindrical surface of the wheel.
However, many wheels use a singular design for the hub cap or center cap that cannot be changed without replacing the entire wheel, and that may not be suitable for all operating conditions (e.g. city driving, off-roading, desert sand, etc.). This limits the options available to the vehicle's owner for both customizing the protection system to better meet changing operating conditions, and for altering the aesthetic appearance of the wheels. Consequently, a need exists for a modular center cap or center cap system that allows the center cap to be altered or replaced without replacing the entire wheel. It is toward such a modular center cap that the present disclosure is directed.